The invention relates to a press having a stand and a tool consisting of at least two parts, on which stand a first holding apparatus for holding a first tool part is mounted. Relative to the first holding apparatus, a second holding apparatus for the counter-tool part can be moved by means of a drive. A handling device having at least one gripping arm is mounted on the said press by means of a bearing element. The invention furthermore relates to a holding device for a tool to be used in this press.
A trimming press analogous to the press stated at the outset is disclosed in German Pat. No. 3,036,333, in which the press has a counter-tool which can be moved horizontally with respect to a stationary tool. The bearing element of the handling device encloses the drive, is located on one of the guide columns of the press, which is also designed as the drive shaft, and is rotatable stepwise through 90.degree. around this column. Out of a total of four gripping arms, two project beyond the outer contour in each of the positions. Out of the four gripping arms, one is in a position for accepting a workpiece which has been produced by a die casting machine and is to be burred, and one is in an insertion position for inserting the workpiece into the press, and a cooling position and a rest or empty position is provided in between.
While in trimming presses only the relatively weak burrs of the workpieces have to be cut off, and this process takes place at relatively long intervals determined by the die casting machine, the situation at higher speeds, particularly in, for example, punch presses, is quite different. There, in fact, it is often necessary to punch through thick metal sheets, and this may take place at very high frequencies. As a result, all parts of the punch press are subjected to strong forces which to date have made it inadvisable to provide handling devices on the press. Furthermore, there does not appear to be any demand for this in automatic punch presses since the "workpieces" are fed in the blank state, i.e. as sheet, by a feed mechanism, whereas the finished workpiece is generally removed without a handling device.
However, what are difficult to handle in such presses and similar ones are the tools themselves. To date, there are two different changing systems on the market. Either the tools are lifted out on roller conveyors (since their weight is generally considerable), for example on a rotary table which is fastened to the floor in front of the press, forms the receiver and blocks access at this point; or the tool emerges, together with part of the table-like stand, on a trolley which can be moved laterally on rails in front of the press. In this case too, the space in front of the press must be kept free for this trolley, and this is particularly inconvenient because, for example, punch presses, particularly at high punching frequencies, are often surrounded by a sound-insulating housing, which in this case has to be specially designed to permit passage of the trolley or acceptance of the tool from the latter.
JP-A-57 199 531 discloses a press of the type stated at the outset. There, both the press itself and the receiving means for a plurality of tools were housed on a common stand. The particular tool desired needed only to be brought into a position opposite the tool holder, whereupon a gripping arm operated by a cylinder pushed it onto the holder. The reverse procedure was used for removing the tool.
Although this known embodiment appeared simple and uncomplicated, it had a large number of disadvantages. The higher the production rate of the press (without even considering true high-speed presses), the greater the vibration the tools in the receiving means had to be subjected to. Since the receiving means had a complicated movement mechanism resembling that of a compound slide (and this with tools weighing several tons), this mechanism was of course rapidly worn down at high punching frequencies. Moreover, the number of tools which could be housed in such a receiving means was of course extremely limited. Another disadvantage was that access to the machine (for example for maintenance work) was very difficult since the entire rear of the press and also part of the sides were occupied by the receiving means.